1. Field of the Invention
The invention relates in general to a circuit arrangement for the automatic closing of a back-up remote feed loop when interruption of the operationally provided remote feed loop occurs which feeds electrical users with DC series feed current whereby the circuit arrangement includes a relay having break contacts mounted with a resistor in a shunt branch and wherein the windings of the relay comprise two partial windings arranged in series with each other.
2. Description of the Prior Art
Circuit arrangements for protecting and feeding circuits by two different power supplies are known as, for example, in the publication Siemens Zeitschrift vol. 45 (1971), entitled Supplement "Nachrichten-Ubertrastechnik" page 102.
Such known circuit serves to close a remote feed loop for series-fed sub-stations when path interruptions occur. So as to maintain the feed in at least one part of the transmission system a relay coil is provided which is connected in each repeater location and the load resistors of the repeaters are connected in different remote feed current paths. The cross-connections to the relay contact results by way of a shunt circuit consisting of respective series connections of at least two diodes connected in parallel to the load resistors and the relay coil.
With these features the definite position of the relay coil and cross-connection in the remote feed path required in the remote feed systems with uniform load distribution for fault localization is independently achieved whether the relay branch of the switching auxiliary is mounted in one or the other remote feed branch. The switching auxiliary comprises a quadripole which is connected with one pair of terminals to the first part of the remote feed loop or with the pair of feed leads facing the signal source and to the second part of the remote feed loop or respectively of the pair of feed leads facing away from the feed location. Because the relay coil and thus the series branch of the quadripole is alternately mounted in the one or the other remote feed current paths from the repeater location to repeater location and the direction of energy flow in the remote feed loop is always the same and a respective change of the direction of energy flow occurs for the quadripole when they are alternately connected in the reverse direction.
If remotely fed stations such as repeater locations of long distance systems contained so-called switching auxiliaries which in the event of a path interruption reclose the remote feed circuit in front of the faulty remote feed section or respectively repeater section, then the relays in the undisrupted path portion necessary for accomplishing this or for giving fault-free operation of the entire transmission path require excitation power necessary for keeping the switch contact open which results in a corresponding voltage drop at the location of each remotely fed station.
It is desirable to keep this voltage drop as low as possible since with a prescribed maximum remote feed voltage the distance which can be remotely fed will be determined and the higher the voltage drop the shorter will be the remote fed distance that can be utilized.
It is known to provide a winding change-over such that when a relay is activated a part of the winding will be shortcircuited such that the system pull and drop-out values for the relay are accomplished. See for example publication entitled Siemens Zeitschrift 45 (1971), Supplement "Nachrichten-ubertragungstechnik" page 102.
In pratice, only a relatively small portion of the winding flux is available for the holding winding of the relay coil and such flux determines the required holding power and thus the voltage drop of the winding required for this purpose.